Star-shaped Poly Research Articles

Fabrication of thermosensitive, star-shaped poly(L-lactide)-block-poly(N-isopropylacrylamide) copolymers with porphyrin core for photodynamic therapy

Thermosensitive, star-shaped porphyrin-cored poly(L-lactide)-block-poly(N-isopropylacrylamide) (SPPLA–PNIPAM) was synthesized via ring-opening polymerization (ROP) and reversible addition–fragmentation chain transfer polymerization (RAFT). The composition and properties of copolymer were discussed based on the results of NMR, IR and GPC. With PNIPAM block length decreasing, the morphology of SPPLA–PNIPAM copolymer in aqueous solution transformed hierarchically from spherical micelles through wormlike micelles to vesicles, and the lower critical solution temperatures (LCST) of the copolymer solutions were determined to be 37.9°, 37.2°, 35.9°, respectively. The in vitro study indicated that SPPLA–PNIPAM showed no significant dark cytotoxicity at concentrations up to 128μg/mL, while showed apparent phototoxicity toward BEL-7402 cancer cells. Considering a high singlet oxygen quantum yield and suitable nominal physiologic LCST, it is expected that the SPPLA–PNIPAM copolymer is a promising stimulus-responsive candidate which has a potential application in photodynamic therapy (PDT).

Preparation of new dendrimer-like star-shaped amphiphilic poly(ethylene glycol)-poly(ϵ -caprolactone) copolymers for biocompatible and high-efficiency curcumin delivery

Novel amphiphilic star-shaped terpolymers comprised of hydrophobic poly(ϵ-caprolactone), pH-sensitive polyaminoester block and hydrophilic poly(ethylene glycol) (Mn = 1100, 2000 g mol−1) were synthesized using symmetric pentaerythritol as the core initiator for ring-opening polymerization (ROP) reaction of ϵ-caprolactone functionalized with amino ester dendrimer structure at all chain ends. Subsequently, a second ROP reaction was performed by means of four-arm star-shaped poly(ϵ-caprolactone) macromer with eight -OH end groups as the macro-initiator followed by the attachment of a poly(ethylene glycol) block at the end of each chain via a macromolecular coupling reaction. The molecular structures were verified using Fourier transform infrared and 1H NMR spectroscopies and gel permeation chromatography. The terpolymers easily formed core–shell structural nanoparticles as micelles in aqueous solution which enhanced drug solubility. The hydrodynamic diameter of these agglomerates was found to be 91–104 nm, as measured using dynamic light scattering. The hydrophobic anticancer drug curcumin was loaded effectively into the polymeric micelles. The drug-loaded nanoparticles were characterized for drug loading content, encapsulation efficiency, drug–polymer interaction and in vitro drug release profiles. Drug release studies showed an initial burst followed by a sustained release of the entrapped drug over a period of 7days at pH = 7.4 and 5.5. The release behaviours from the obtained drug-loaded nanoparticles indicated that the rate of drug release could be effectively controlled by pH value. Altogether, these results demonstrate that the designed nanoparticles have great potential as hydrophobic drug delivery carriers for cancer therapy. © 2015 Society of Chemical Industry

Star-shaped PCL/PLLA blended fiber membrane via electrospinning

Electrospun fiber mesh has been a candidate for guided bone regeneration membrane. However, its poor mechanics property has been limited in clinical application. In this study, various star-shaped poly(ε-caprolactones) (PCLs) are successfully synthesized by ring-opening polymerization and mixed with poly(l-lactide) (PLLA) to be made into blended membranes through electrospinning. Their corresponding properties are evaluated including morphology, thermodynamics, mechanics, and cytotoxicity. The blended fibers show smooth surface and well-distributed structure, which have slight differences in morphology with the change of arm number of star-shaped PCL. Crystallization of the fibrous membrane is influenced by star-shaped PCLs. Glass temperature drops from 64.23 °C for pure PLLA membrane to 53.62–49 °C for the blended membranes. The membranous tensile strength is depended strongly on star-shaped PCLs. The tensile strength goes up with arm number increasing; on the contrary, at the same arm number, the mechanics strength decreases with molecular weight increasing. And the fibrous membrane containing 20 wt.% star-shaped PCL shows better mechanics property compared to the other membranes. The star-shaped PCL/PLLA fiber membrane is not cytotoxicity.

Thermosensitive gold nanoparticles based on star-shaped poly(N-isopropylacrylamide) with a cubic silsesquioxane core

Thermosensitive gold nanoparticles based on star-shaped poly(N-isopropylacrylamide) with a cubic silsesquioxane core

Rational design of shear-thinning supramolecular hydrogels with porphyrin for controlled chemotherapeutics release and photodynamic therapy

An amphiphilic porphyrin-cored, star-shaped poly (ε-caprolactone)-b-poly (ethylene glycol) (SPPCL-b-PEG) copolymer was synthesized and used as a building block for constructing supramolecular hydrogels. With the aid of α-cyclodextrin (α-CD), thixotropic and reversible supramolecular hydrogel could be formed by copolymers based on the host–guest inclusion complexation (IC). Due to the biodegradable and biocompatible properties, this IC-based supramolecular hydrogel was used as carrier for doxorubicin (DOX) delivery systems. The release results presented a triphasic drug-release profile and the release of this system lasted more than 3weeks. Also, upon irradiation with light (650nm), cytotoxic singlet oxygen (1O2) could be generated by porphyrin core and easily released from hydrogel matrix. Considering that both sustained-release drug delivery of hydrogels and porphyrin for photodynamic therapy (PDT) were achieved in a combined compound, this shear-thinning supramolecular hydrogel with porphyrin was elaborately designed as a promising replacement therapy to medium or advanced cancer for surgery.

Synthesis and characterization of four- and six-arm star-shaped poly(ε-caprolactone)-b-poly(N-vinylcaprolactam): Micellar and core degradation studies

Star-shaped copolymers with four and six poly(ε-caprolactone)-block-poly(N-vinylcaprolactam) (S(PCL-b-PNVCL)) arms were successfully synthesized by combining ring opening polymerization (ROP) of ε-caprolactone (CL) and reversible addition-fragmentation chain transfer (RAFT) polymerization of N-vinylcaprolactam (NVCL). The resulting star copolymers were characterized using 1H NMR, GPC and UV–vis. The numbers of arms in the star-shaped PCL-b-PNVCL block copolymers were demonstrated using degradation studies under acidic conditions, and the individual PNVCL chains were characterized by GPC and 1H NMR. In aqueous solution, star-shaped PCL-b-PNVCL block copolymers self-assembled into large aggregates or micelles with sizes varying from 54 to 300nm, depending on the molecular weight of the copolymer and the relative lengths of the hydrophobic and hydrophilic segments. Micelles were characterized by atomic force microscopy (AFM), dynamic light scattering (DLS) and scanning electron microscopy (SEM).

Novel poly(tetramethylene ether)glycol and poly(ε-caprolactone) based dynamic network via quadruple hydrogen bonding with triple-shape effect and self-healing capacity.

A novel dynamic network was successfully prepared via self-complementary quadruple hydrogen bonding through Upy-telechelic poly(tetremethylene ether) glycol (PTMEG) and four-arm star-shaped poly(ε-caprolactone) ((4)PCL) precursors. The structure and the dynamic feature were identified by FT-IR and (1)H NMR. The differential scanning calorimetry (DSC) analysis indicated that the crystalline PCL and PTMEG segments show a separated melting peak, and the aggregation of Upy dimer was also observed. The dynamic mechanical analyzer (DMA) test reveals that the storage modulus of the network drops evidently across the thermal transition. These characteristics of the network ensure that it exhibits a triple-shape effect, and the composition of the network influences the performance of shape memory effect. The variation of the fixing ratio of the network in each deformation step is quite according to the crystallinity of the dominant segment. The reversibility of the quadruple hydrogen bonding between Upy dimer endues the network with self-healing capacity, and the damage and healing test of the network revealed that increasing the content of the PTMEG segment will be of benefit to self-healing performance.

Molecular and structural characterization of hybrid poly(ethylene oxide)-polyhedral oligomeric silesquioxanes star-shaped macromolecules.

Octafunctionalized spherosilsesquioxanes (Q8M8(H)), decorated with Si-H functions, could be used to design, by coupling via hydrosilylation with α-methoxy-ω-undecenyl poly(ethylene oxide)s (PEOs), organic-inorganic nanocomposite structures. (1)H, (13)C, and (29)Si NMR; size exclusion chromatography; and Fourier transfrom infrared spectroscopy were used to follow the grafting reaction and determine the molar mass and the functionality of the different species. Hybrid star-shaped poly(ethylene oxide)s of precise molar mass and functionality could be isolated by fractional precipitation of the raw reaction product. Absolute molar masses of the purified star-shaped PEOs, calculated with the assumption of a functionality of 8, were comparable when measured by light scattering in methanol and by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Small-angle X-ray scattering was employed to determine their molecular and structural characteristics, representing the versatility and innovative aspect to this study. Both differential scanning calorimetry and optical microscopy were utilized to elaborate and analyze the thermal properties and crystallization, respectively, of the hybrid stars. Further ongoing work is being carried out currently to investigate and foresee the use of longer PEO branches onto the core.

Star-shaped poly(2-methyl-2-oxazoline)-based films: rapid preparation and effects of polymer architecture on antifouling properties.

Development of surfaces with antifouling properties is of great interest in biomedical applications. In this paper, the research was aimed at rapid preparation of poly(2-methyl-2-oxazoline)-based antifouling coating. We designed and synthesized a set of well-defined multiarm star copolymers hyperbranched poly(ethylenimine)-graft-poly(2-methyl-2-oxazoline) (PEI-g-PMOXA) with different PMOXA grafting ratios and chain lengths. The cytotoxicity of the polymer was tested and the PMOXA-based films were successfully deposited rapidly onto substrates via a simple one-step dopamine-assisted codeposition method. The effect of polymer architecture (linear PMOXA with different molecular weights, star PMOXA with different PMOXA grafting ratios and arm lengths) on deposited films with respect to their deposition kinetics, surface composition, wettability, morphology, cytotoxicity, and antifouling properties was investigated systematically. The antifouling properties of PMOXA-based films were found to be dependent on the surface PMOXA chain densities, which were controlled by the PMOXA grafting ratios and chain lengths. Moreover, the star PMOXA structures gave the surfaces with higher PMOXA chain densities and enhanced antifouling properties compared to the linear ones. Among the star copolymers, PEI-g(70)-PMOXA(5K)/polydopamine and PEI-g(70)-PMOXA(7K)/polydopamine deposited films showed the highest resistance to protein adsorption (96-99% relative to the bare gold surface) and cell attachment (97-99% relative to the bare glass surface), as well as complete inhibition against platelet adhesion. At last, the stability test results showed that the PMOXA-based film exhibited superior stability in long-term applications than the poly(ethylene glycol)-based film.

Efficient size control of copper nanoparticles generated in irradiated aqueous solutions of star-shaped polyelectrolyte containers.

The formation of copper nanoparticles (Cu-NPs) in irradiated aqueous solutions of star-shaped poly(acrylic acid) (PAA) were studied at two pH values. Transmission electron microscopy (TEM) demonstrates that the star-shaped macromolecules loaded with Cu(2+) ions can act as individual nanosized containers providing a perfect control over the size and size distribution of Cu-NPs. Electron paramagnetic resonance (EPR) and optical spectroscopy show a transformation of mechanisms controlling the reduction of Cu(2+) ions and the further formation of Cu-NPs. At pH 2.9, Cu-NPs are formed from the aquacomplexes of Cu(2+) ions through homogeneous nucleation. At pH 4.3, the formation of Cu-NPs occurs inside macromolecular containers loaded with Cu(2+) ions, which are bound to carboxylic groups of the polyelectrolyte. In the latter case, Cu-NPs apparently ripen from preformed hydrated Cu2O seeds, which are thought to result from the ultrasmall (Cu(2+))m(OH(-))k(COO(-))n species, thus implying a heterogeneous nucleation.

Synthesis and thermoresponsive properties of four-arm star-shaped poly(N-isopropylacrylamide)s bearing covalent and non-covalent cores

We succeeded in synthesizing a series of poly(N-isopropylacrylamide)s with linear and four-arm star-shaped structures and clarified their thermoresponsive properties.

Thermal and Mechanical Properties of Biodegradable Star-Shaped/Linear Polylactide Stereocomplexes

The 6-arm star-shaped poly(L-lactide) (6PLL)/linear poly(D-lactide) (1PDL) stereocomplex films were prepared by the solvent casting method. The influences of the 6PLL/1PDL blend ratios (75/25, 50/50, and 25/75 w/w) and 1PDL molecular weights (15,000, 30,000, and 60,000 g/mol) on the thermal and mechanical properties of the stereocomplex films were investigated. The 6PLL and 1PDLs had a single melting temperature (Tm) of homocrystallites at 174°C and 167°C, respectively. The 6PLL/1PDL blends had twoTms: a lowerTmof homocrystallites (160–173°C) and a higherTmof stereocomplex crystallites (219–228°C). The stereocomplex crystallinity and mechanical properties of the 6PLL/1PDL blend films were higher than those of 6PLL and 1PDL and were the highest in the 50/50 (w/w) blend ratio. However, the stereocomplex crystallinity of the 50/50 (w/w) 6PLL/1PDL blend films decreased and the mechanical properties increased as the molecular weight of 1PDL increased.

Star-shaped PHB-PLA block copolymers: immortal polymerization with dinuclear indium catalysts.

The first example of a one-component precursor to star-shaped polyesters, and its utilization in the synthesis of previously unknown star-shaped poly(hydroxybutyrate)-poly(lactic acid) block copolymers, is reported. A series of such mono- and bis-benzyl alkoxy-bridged complexes were synthesized, fully characterized, and their solvent dependent solution structures and reactivity were examined. These complexes were highly active catalysts for the controlled polymerization of β-butyrolactone to form poly(hydroxybutyrate) at room temperature. Solution studies indicate that a mononuclear propagating species formed in THF and that the dimer-monomer equilibrium affects the rates of BBL polymerization. In the presence of linear and branched alcohols, these complexes catalyze well-controlled immortal polymerization and copolymerization of β-butyrolactone and lactide.

Thermo-responsiveness and biocompatibility of star-shaped poly[2-(dimethylamino)ethyl methacrylate]-b-poly(sulfobetaine methacrylate) grafted on a β-cyclodextrin core

CDPDS star polymers exhibit tunable UCST behavior by varying arm density, solution pH and NaCl concentration, and can be good candidates used in biomedical relevant fields as well.

Effect of arm number of poly(acrylic acid) on cloud point temperature of poly(2-ethyl-2-oxazoline)

The phase transition behavior of poly(2-ethyl-2-oxazoline) (PEtOx) under complexation with star-shaped poly(acrylic acid) (PAA) having various arm numbers (two, three, four, and six) has been studied by turbidity and laser light scattering measurements. The change in cloud point temperature (T cp) of PEtOx was monitored as a function of pH, ionic strength, and arm number of the star polyelectrolyte. The shift in T cp to a lower value than that of pure PEtOx was more pronounced at pH 4.2 (pH pKa ), when the acid moieties are partially ionized. Dynamic light scattering showed that these complexes may have micellar core-shell type structure with a mean hydrodynamic radius (R h) ranging from 12 nm to ∼200 nm depending upon the temperature. Significant shift in T cp was observed for six-arm star poly(acrylic acid) complexes at both pH values. This change in the T cp is accredited to the differences in the driving forces of phase transition, including hydrogen bonding between carboxylic acid groups of PAA and the carbonyl moiety of PEtOx as well as the hydrophobic interactions.

Biohybrid networks of selectively desulfated glycosaminoglycans for tunable growth factor delivery.

Sulfation patterns of glycosaminoglycans (GAG) govern the electrostatic complexation of biomolecules and thus allow for modulating the release profiles of growth factors from GAG-based hydrogels. To explore options related to this, selectively desulfated heparin derivatives were prepared, thoroughly characterized, and covalently converted with star-shaped poly(ethylene glycol) into binary polymer networks. The impact of the GAG sulfation pattern on the network characteristics of the obtained hydrogels was theoretically evaluated by mean field methods and experimentally analyzed by rheometry and swelling measurements. Sulfation-dependent differences of reactivity and miscibility of the heparin derivatives were shown to determine network formation. A theory-based design concept for customizing growth factor affinity and physical characteristics was introduced and validated by quantifying the release of fibroblast growth factor 2 from a set of biohybrid gels. The resulting new class of cell-instructive polymer matrices with tunable GAG sulfation will be instrumental for multiple applications in biotechnology and medicine.

Deuterium Isotope Effect on Solution Behavior of Thermoresponsive Star-Shaped Poly(2-isopropyl-2-oxazoline)

Thermosensitive star-shaped poly(2-isopropyl-2-oxazoline) (molar mass M≈21000 g mol−1) in D2O solution was studied by the static and dynamic light scattering methods. The behavior of the polymer investigated in deuterated water is similar qualitatively to that observed previously in undeuterated water. At the same time, the considerable quantitative changes of polymer behavior in D2O were seen. Deuterium substitution of solvent affects the phase transition temperature by decreasing its value by 1°C. The temperature interval of phase transition in D2O solution expands (by about 1°C) in comparison with that in H2O solution.

Octa-armed star-shaped poly(ε-caprolactone)s with a phthalocyanine core by ring-opening polymerization: Synthesis and characterization

A series of hydroxyl-terminated octa-armed star-shaped poly(ε-caprolactone)s (8SPCL1–3, represented as 5, 6 and 7, respectively) with an initiator core of 2,3,9,10,16,17,23,24-octakis(3-hydroxypropylmercapto)phthalocyaninatozinc(II) (4) was synthesized by the ring-opening polymerization of ε-caprolactone using tin(II) 2-ethylhexanoate as the catalyst. The obtained star-shaped polymers were characterized by FT-IR, 1H NMR, GPC and UV–vis spectroscopy. The measured intrinsic viscosities of all polymers were used to calculate the number-average molecular weight. The fluorescence of polymers 5–7 was studied. The changes in the visible spectra of 7 were investigated by increasing the concentration and adding methanol and cations such as Ag+, Hg2+, or Pb2+. The electrical conductivities of the polymers measured in vacuum and in air were between ∼10−9 and 10−6Sm−1. DSC and polarized optical microscopy techniques were used to evaluate the crystalline behavior of 5–7. The thermal stability of 5–7 was investigated by TGA.

Glycosylated star polypeptides from NCA polymerization: selective binding as a function of degree of branching and glycosylation.

Star-shaped polypeptides were synthesized via N-carboxyanhydride (NCA) polymerization initiated from various generations of PPI dendrimers. Molecular weight, arm length, and arm density were readily controlled to afford a series of star-shaped poly(glutamic acid) derivatives. Glycosylation of star-shaped poly(glutamic acid) resulted in the formation of a diverse range of glycopolypeptide architectures with tuneable degree of sugar conjugation. The secondary structure of the branched glycopolypeptides was studied as a function of the degree glycosylation. The bioactivity of the described glycopoly-peptides toward the lectin ConA was investigated and was shown to be architecture dependent.

Self-assembly of star-shaped poly(2-isopropyl-2-oxazoline) in aqueous solutions

Eight-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) with calix[8]arene core (M ≈ 20,000 g mol−1) was studied by turbidimetry and light scattering in aqueous solutions within concentration c ranging from 0.002 to 0.19 g cm−3. The lower critical solution temperature (LCST) for PiPrOx is about 10 °C lower than for the linear analog. PiPrOx forms two types of particles at room temperature. The specie responsible for the fast mode is single macromolecules or 2–3 ones joined in aggregate with a hydrodynamic radius of 4.9 nm, irrespective of concentration. On heating, at first, growth of a large aggregate fraction was observed without variation of their hydrodynamic radii R h (s). Then, R h (s) increased up to 800 nm at c = 0.002 g cm−3, while the fast mode disappeared. At all concentrations, the third middle mode with a size ranging from 9 to 40 nm was registered. It was observed in a very narrow temperature interval near the cloud point. The hydrodynamic radii of species and their fraction in solution were monitored as a function of time after the change in temperature.